Abstract

Planar partitions are frequently used to model, among others, land cover, cadastral parcels and administrative boundaries. In practice, they are often stored as a set of individual polygons to which attributes are attached, e.g. with the Simple Features paradigm, causing different errors and inconsistencies, e.g. gaps, overlaps and disconnected polygons, which are introduced during their creation, manipulation and exchange. These errors severely hamper the use of planar partitions in other software, e.g. due to false assumptions causing erroneous calculations. Existing approaches to validate planar partitions involve first building a planar graph of the polygons and enforcing constraints, then repair is done by snapping vertices and edges of this graph. We argue that these approaches have many shortcomings in terms of complexity, numerical robustness and difficulty of implementation, and do not guarantee valid results. Furthermore, they are semi-automatic, requiring manual user intervention. We propose in this paper a novel method to validate and automatically repair planar partitions. It uses a constrained triangulation of the polygons as a base - which by definition is a planar partition - and only simple operations are needed, i.e., labelling of triangles, to both validate and repair. Perhaps the biggest advantage of our method is that we can guarantee that a planar partition is valid after repair. In the paper we describe the details of our method, our implementation, and the experiments we have done with real-world datasets. We show that our implementation scales to big datasets and that it offers better capabilities and overall performance than existing solutions.